The invention relates to a method and a device for preparing, manipulating, and processing a staple wire in an apparatus for stapling sheets, in which the staple wire is fed from a supply roll to a stapling device, a wire length dependent on the sheet stack thickness is cut off and shaped into a staple, and the staple is driven into the sheet stack.
In the case of a device of the type disclosed by U.S. Pat. No. 4,898,314, the staple wire is arranged in a cassette, and a flexible guide tube, which is joined to the cassette and whose outlet is configured as a coupling to which the wire end is attached, is provided. The staple wire is joined by means of said coupling to a wire transport device, arranged in the region of the stapling device, which transports the staple wire into the stapling device. With this known device, a complete unit consisting of cassette, guide tube, and coupling must be replaced each time the supply of staple wire is to be replenished. When a new supply of staple wire is inserted, the coupling joined to it must be delivered manually to the immediate vicinity of the stapling device.
In another device for delivering the leading end of the wire to a stapling device (U.S. Pat. No. 4,722,467), a threading-in device which has a funnel-shaped inlet opening for the wire end is provided directly upstream from the stapling device. The wire end is introduced manually into said inlet opening, and pushed forward until the leading end arrives at visible marks, from which point wire transport on the part of the stapling unit becomes effective. At the beginning of the threading-in process, a clamping device for the wire must be moved manually into an ineffective position, and, once the threaded-in position is reached, must be moved into a clamping position which prevents the staple wire from slipping back.
In the case of a loading device for a staple wire roll disclosed in Research Disclosure No. 29834, May 1988, a displaceable holder is provided on which the staple wire roll is mounted. The holder is movable from a location arranged inside an apparatus into a pulled-out location in which the staple wire roll is positioned to be accessible for replacement. With this device, the leading end of the staple wire must be pushed manually into a flexible tube leading to a transport device of a stapling head until the wire end has arrived at the transport device.
EP-B-0 013 164 has disclosed a stapling device in which the staple wire coming from a supply roll is transported, as a function of the sheet stack thickness to be stapled, by means of a transport device having clamping elements, and positioned centeredly on the stapling head. The operation of the clamping elements of this known device can be impaired, by soiling and/or by wear of the staple wire, in such a way that reliable transport of the staple wire can no longer be ensured.
Also known is a stapling device (U.S. Pat. No. 4,318,555) in which transport of the staple wire is accomplished by motor drive in such a way that a sensor detects the number of sheets to be stapled, and then sets in motion a first transport device for a shorter wire segment or a second transport device for a longer wire segment. This device does not, however, allow any intermediate sizes of wire segment for a staple size matched precisely to the particular sheet stack thickness.
With some of these known and in some cases relatively complex devices, it is necessary to deliver the wire end by hand to the immediate vicinity of the stapling device. Since the stapling device of a stapling apparatus, which can for example be arranged in a finishing device for folding, collating, stapling, and depositing sheet stacks, is as a rule arranged at a poorly accessible point in the apparatus, replenishing the staple wire supply is, with the known devices, so complex and laborious that it can be performed only by trained personnel.